This invention relates to a strut mount disposed at an attachment portion of a buffer to a vehicle.
In general, in a suspension system of an automobile, etc., a so-called strut mount is disposed at an attachment portion of a buffer to a vehicle body, in order to control vibration, etc. propagated from wheels to the vehicle body.
FIG. 6 shows an example of the strut mount. The strut mount comprises an inner cylinder 101 in which a piston rod of the buffer is fixed, an outer cylinder 102 attached to the vehicle body, and a rubber elastomer 103 interposed between the inner and outer cylinders to dampen input vibration, and a bolt 106 inserted into a bolt hole 105 thereof from below is press fitted and secured to an attachment piece 104 of the outer cylinder 102. With the bolt 106 lifted up so as to insert into a bolt hole 108 of the vehicle body""s outer cylinder attachment plate 107 from below and a nut tightened from above the outer cylinder attachment plate 107, the strut mount will be attached to the vehicle body only by attachment working from above.
In order to raise rigidity and improve running properties, the strut mount shown in FIG. 6 is constructed so that the attachment piece 104 of the outer cylinder 102 and the outer cylinder attachment plate 107 of the vehicle body are curved in the form of a sphere, and that each bolt 106 press fitted and secured to the attachment piece 104 is oriented toward the inclined direction, respectively, against the direction of movement (perpendicular) when the strut mount is lifted up. For that purpose, the bolt hole 108 on the outer cylinder attachment plate 107 is made larger so that the bolt 106 oriented toward the inclined direction can be inserted.
However, when the bolt hole is large, it is apprehended that there occur problems related to bolt tightening such as looseness. Therefore, a means of inserting the bolt, without making the bolt hole larger, and tightening the bolt only by operations from above is pursued.
The present invention has been made in view of the subjects described above, and it is an object of the invention to provide a strut mount intended to insert a bolt, without making the bolt larger, and tighten an attachment piece of an outer cylinder at the underside of a vehicle body""s outer cylinder attachment plate, with a bolt, only by operations from above, by providing a nut at the underside of the outer cylinder attachment piece and screwing the bolt into the nut from upside the outer cylinder attachment plate of a vehicle body.
When providing the nut for the attachment piece of the outer cylinder, a technique that a small hole is drilled at the prescribed position on the attachment piece of the outer cylinder, a burr is formed (burring working) downwardly around the circumferential edge of the hole as a cylindrical portion, and an inner circumferential surface of the cylindrical portion is tapped and cut as screw threads to serve as a nut, also comes to mind. However, such technique makes its working difficult and complicated. Furthermore, in order to elongate the nut of a given diameter and cut the required number of screw threads, it is necessary to thicken the outer cylinder, with the result that the weight of the components grows heavier.
Otherwise, as for the method of welding a nut on the underside of the attachment piece of the outer cylinder, in order to avoid deterioration of rubber elastomer due to welding heat, it is necessary to weld the nut before working the strut mount or to escape welding heat by masking around the nut of the attachment piece, whereby making the strut mount working difficult and complicated.
Accordingly, the present invention adopts a nut securing means of making the thickness of the outer cylinder thinner to lightweight the components, without causing difficult and complicated working, and capable of maintaining the durability of rubber elastomer, by caulking and securing the nut on the underside of the attachment piece of the outer cylinder.
When caulking and securing the nut to the attachment piece of the outer cylinder, either upsetting on the nut side or diminishing in diameter the nut attachment hole of the outer cylinder can be adopted.
In case of upsetting on the nut side, the nut attachment hole is drilled on the attachment piece of the outer cylinder, on the other hand, a cylindrical portion is provided continuously from the nut portion for the caulking nut: the cylindrical portion is inserted into the nut attachment hole from the underside of the attachment piece of the outer cylinder; after that, when the cylindrical portion is upset and caulked and secured to the nut attachment hole, an outer circumferential surface of the cylindrical portion is stuck fast to an inner circumferential surface of the nut attachment hole, thus sticking the nut on the underside of the attachment piece of the outer cylinder.
In case where the nut attachment hole is diminished in diameter, with the cylindrical portion of the caulking nut inserted into the nut attachment hole from the underside, by pressurizing the circumference of the nut attachment hole from the direction square to the plate surface of the attachment piece of the outer cylinder, the inner circumferential surface of the nut attachment hole is stuck fast to the outer circumferential surface of the cylindrical portion to caulk and stick the nut on the underside of the attachment piece of the outer cylinder.
At this time, provided that the outer circumferential surface of the cylindrical portion of the caulking nut is corrugated, an extra wall surrounding the nut attachment hole cuts into the corrugated outer circumferential surface of the cylindrical portion as the nut attachment hole is diminished in diameter, the extra wall acts as a steady rest to restrain the caulking nut from turning together with the bolt.
When the attachment piece of the outer cylinder and the outer cylinder attachment plate of a vehicle body are curved in the form of a spherical surface, the aforementioned means may appropriately be used for a strut mount. Where the form of a spherical surface denotes a curved surface constituting a part of a sphere.